The invention relates to a transporting device for vacuum coating installations with several stations and with roller systems for the guidance and advance of essentially two-dimensional substrate holders in a vertical position along a given transport path through the stations.
The substrate holders used are either plates with cutouts shaped to correspond to the substrates or frames with struts, to which the substrates are attached. In general, a substrate holder serves to carry a large number of substrates. Since the thickness of such a plate or frame is very small in relation to its principal plane, such a substrate holder can be referred to in a simplified fashion as two-dimensional.
Provided that the substrates are to be coated on only one side, the substrate holder is passed through the coating installation with its principal plane in the horizontal position and, when cathode sputtering is used as the coating method, is coated from above. For this purpose, the substrate holders, several of which are always passed cyclically and consecutively through the coating installation, lie on transporting rollers as they are passed through said installation, at least some of the rollers being driven. Such roller systems do not create any problems with respect to the coating process.
For the two-sided coating of the substrates however, the substrate holders are generally passed through the installation with their principal plane aligned in the vertical direction. With methods employed in the past, the substrate holders have been provided at their upper and lower longitudinal edges with prismatic longitudinal grooves, with which in each case upper and lower guide rollers meshed. However, the substrate holders are also coated during the coating process, the thickness of the coating growing in the course of time, until separation of layer particles takes place at isolated places. This separation is promoted appreciably by the guide rollers and especially the upper guide rollers lead to a situation in which the substrates are passed through a shower of layer particles, which have flaked or peeled off, so that a defective coating with the feared pin holes results.